@width1: 100px;
@width2: 200px;
@height: 300px;
@boolean: boolean(2 > 1);
@step: range(1,12,1);  // 1,2,3,4,5,6,7,8,9,10,11,12

.box {
  width: if(@boolean, @width1, @width2);
  height: @height;
}

each(@step, {
  el-@{value} {
    width: 8.3% * @value;
  }
})

